paint-volume: Don't try to complete a completed volume
paint-volume: Don't try to complete a completed volume

If we do project() → get_bounding_box(), we'll try to complete the
volume twice, which whacks out all the lazily computed vertices.

Reviewed-by: Robert Bragg <12e9293ec6b30c7fa8a0926af42807e929c1684f@linux.intel.com>

collects/clutter,djdeath/clutter-multithreaded,Distrotech/clutter,djdeath/clutter-android,Distrotech/clutter,jigpu/clutter,djdeath/clutter,Distrotech/clutter,djdeath/clutter-android,ebassi/clutter,jigpu/clutter,djdeath/clutter,Distrotech/clutter,GNOME/clutter,djdeath/clutter,ebassi/clutter,kerrickstaley/clutter-vala,jigpu/clutter,ebassi/clutter,djdeath/clutter,djdeath/clutter-multithreaded,jigpu/clutter,kerrickstaley/clutter-vala,collects/clutter,djdeath/clutter,heysion/clutter-clone,GNOME/clutter,GNOME/clutter,djdeath/clutter-multithreaded,heysion/clutter-clone,collects/clutter,ebassi/clutter,ebassi/clutter,jigpu/clutter,kerrickstaley/clutter-vala,Distrotech/clutter,heysion/clutter-clone,heysion/clutter-clone,jigpu/clutter,GNOME/clutter,kerrickstaley/clutter-vala,Distrotech/clutter,collects/clutter,djdeath/clutter-android,collects/clutter,GNOME/clutter,heysion/clutter-clone,djdeath/clutter-android,djdeath/clutter-multithreaded,djdeath/clutter,djdeath/clutter-android